Pythagorean Theorem
by WookieCookie
Summary: Hiro remembers sleeping in his bed with Mochi napping flat on his stomach. He certainly doesn't remember waking up to a world full of corpses walking around. Zombies AU No Slash


**Warnings: _Not beta, grammatical errors, and author._**

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There's something not right with the way the foreign, unsolicited solid surface coils beneath his skin because Hiro can almost scarcely remember that - blames it on the many dumps of his college projects - he, at least, throws his completely worn and limp body on a mattress. In his room. In his now empty, perhaps begrudgingly cold room.

(It seems void without _his_ presence in there)

Mochi's flat on his stomach, catnapping like the pudgy ball fits there as Aunt Cass turns off the lamp for him.

Yet now as he tiredly flutters his lids open, he can see a dark mahogany ceiling and a dusty clouded room. Dirty, cluttering idle objects here and there and somehow the only source of light is the dimmed-light from the window barred shut by boards (it's night, he evaluates). The nails sticking out at the edge is enough of an answer that the boards are secured shut in such a clumsy haste.

He wonders why.

Then he looks down and - oh good god, what is he wearing? A rugged white-brownish shirt, with few cuts at the middle and a dirty, baggy dark pants. The zippered pockets are there but they look like they have seen better days. His shoes are of old sneakers, terrible incisions adorn the design. No laces.

What's going on?

Is this some kind of a joke?

_Scratch scratch scratch _

Hiro looks to the window, through the small hole and outside into the faded view of moon and pale sky. There, he sees hands clawing at the walls, desperately trying to find a way in, follows by a growl - several of them - and Hiro swears this is not how he plans to start his morning.

Hiro walks around the house, having planned to explore the upper floor. It looks uninhibited but it's fortified in. No one's going to bust in anytime soon and Hiro guesses that no one's going to barge out too. It's fine by him. If he goes out, those things, whatever they are, stagnant and reek like death will get to him. And you see,

-Hiro may have lost one good thing in his life that has retained him strong and stride through the lonely life, but he also has many good things left for him to kick and fight for his strong heart. He's fifteen now. A year after the flame. A year after he's gained something new because whatever you've lost, you'll gain something back in return to stitch the scarred helical in your heart.

(Or so Hiro hopes. Maybe it's not working for him because he doesn't want the loss to be healed.)

A year and he still desperately misses _him_. The longing will never stop.

Maybe-

"Hiro?"

The young inventor pauses at the landing, stopping himself from taking another step to the second floor.

"Hiro, darn it! You shouldn't be sneaking around like that-"

Hiro doesn't dare to turn. His grip on the rail cracks.

He knows that voice. He's known it his entirely existence. And he hates the familiarity in _his_ voice.

What's going on?

A sigh. Slow footsteps. A rustle of clothing. Another tired sigh. More slow footsteps and then the stranger is there. At his side, on his full height as he surveys down at Hiro cautiously. This stranger who's wearing his brother's face and using his voice like it belongs to him.

The stranger pulls Hiro away from the stairs and straight into his chest, trembling but strong arms capture him in a soft clinch. He tucks Hiro's head under his chin as he breathes shakily into the messy black hair. Hiro shudders.

He doesn't return the hug. His arms on his side. Hiro stays there, mind gearing up to exploit the utmost logical for this situation. He should have done it sooner but somehow, earlier he's kind of hoping Fred is playing another prank on him. Now, he doesn't know anymore.

Tadashi's not here.

Tadashi's dead.

He's too numbed to reciprocate, to think.

"What's wrong?" The man with Tadashi's face speaks. He's not donning his favorite cap, wearing just a simple, dirty grey jacket and a shade of military cargo pants with his crew cut hair covers in white cottons. Hiro will later on identify them as snow. There are dual asymmetrical scars on his right cheek, just below his eye. They look timeworn.

This Tadashi stares at Hiro with that similar concern, similar crease between the brows, similar lopsided frown and annoyingly similar twist of expression. This man appears as if he's gone against a pack of wolves, with only a thin metal bar as his protector.

Then the man smiles in a small grace. He kisses Hiro's forehead and says, "Stop worrying me like that, knucklehead."

_Knucklehead knucklehead knucklehead_

This man might not be his brother. Hiro might be losing his mind. Heck, perhaps he's detained in an asylum right now, caged by leather belts to keep him from harming himself.

Yet right now, all Hiro can do is to dig himself deeper into the hug, hoping he can create a nest there and just never leave. Clip his wings if he were a bird so he couldn't roam from this small, so-achingly-needed spot. He wants to cry. Can he? Can he do it?

What's going on?

Hiro inhales this Tadahi - Creepy, he knows - and he smells like a clattered woods and musky scent of mud and rain. He doesn't smell like home, comfy couch or picket fence. Or maybe an oil. This Tadashi has been away from his home for quite a long, long time.

He-

_Thud thud thud scratch growl break_

Both boys jump at the intruding sound, Hiro more than Tadashi and by the time Hiro shifts to look at the other man, Tadashi is already treading away carefully. A cudgel tight in his hand and if Hiro focuses closer at the view, he can detect a wet hue of dried blood. He doesn't question it. Hiro makes a motion to follow Tadashi. More out of curiosity than naive courage.

"Stay." His brot -... This Tadashi hisses at him, pointing one finger exaggeratedly in Hiro's chest.

"What? No!"

_"Shh." _Tadashi presses.

"No. I'm not letting you go alone-" not when they're seeking shelter in an abandoned spot that's mirroring the condition of a house ransacked by heavy storm. No way.

"This is not a request, Hiro. It's an order. One that you will acquiesce." There's no old-Tadashi in that tone. This Tadashi, when giving command is speaking like he's- Hiro blinks. He studies this Tadashi. Really studies him. The fit muscles and broader chest. Sharp, military stance and haunted eyes.

It dawns on him that he sees a trace of a man who is created in a war. Not a man who spends his life in a lab, basking himself in tools and new creations.

This Tadashi may or may not be a former soldier.

"I-"

"Stay. And don't make a noise." Tadashi pulls put a combat knife from his left boot - yep, really a former soldier - and gently puts it in Hiro's hand. "In case if I don't come back-"

_Panic breathing no don't please come back no don't go not again_

"-you run, okay? Remember the rule I've made specifically for you: Hide first, shoot later." And Tadashi's off, taking a wary peek before disappearing in a sharp turn around the corner.

Inhales in.

Inhales out.

In.

Out.

In.

Out.

What's going on?

He glares at the knife in his hand. It glimmers, beckoning Hiro to use it. To be prepared and killed whatever it is that rushes at his way. Hiro never kills. Almost. But never. He has a nil grasp of the situation, and what he's supposed to fear.

Maybe the ones that clawing and gurgling outside?

_Creak creak creak crack growl_

Hiro quickly bends down on one knee, gaze scatters over his surroundings. Whatever those things outside, they're in here with him now. Hiro can smells something decomposing in the air and he takes a slow step back to the wall behind him. He wants nothing to ambush him from his blind spot.

_Creak creak growl creak stop_

He takes a breath. He's a crime fighter, for the love of- he can do this.

(But that's only because you have Baymax and the team to watch over your back. Your gadgets to keep you safe.)

Hiro twists the knife for an easy slash, and sips a breath. He squints for a better access at the parameter, scanning the area a few feet away from him. There's a slow movement there, dragging limbs and grimacing noises.

Hiro creeps closer; drawing his eyes near to get a clear display of what it is that-

Holy-

Hiro bites his lower lip. Don't gasp or scream. Just. Don't.

If the smell is not a dead giveaway, the exterior looks definitely do.

Rotten flesh.

Mutilated bones.

White, dead eyes.

What's going on?

Those creatures look like a walking cadaver, sniffing and licking at the atmosphere, searching for a source of something (sustenance?), moldy skin dangles from every inch of their body. They crunch and burble at each other.

No.

He can't be here.

He needs to find a safe spot.

Hiro's just about to stand when a quick rush throttles toward him and Hiro has only a second to look to his right before a figure of a mutilated woman in long, jet hair jumps on him. The glint of her (it?) nails screams fatal.

The knife in his hand clatters free from his hold.

Hiro's straddled on the floor.

That thing is on top of him, struggling to get a portion of _Hiro_.

The creature is snarling in his face, showing her sewn mouth, as if someone's been trying to clip it closed. Hiro strains; he fights it off with his arms being the only ones that keep pushing at her (its?) chest. It doesn't work in his favor when she (it?) unseals her jaws open and something like meat clings on her (its?) pallid teeth.

_Creak rush growl_

Hiro turns his face sideway to avoid the falling dribble; her (it?) lips are now only an inch apart from his shoulder. On his left, Hiro can now fully see the rest of those creatures coming toward the exhibiting noise.

Darn darn darn darn the knife? Where-

_Rip rip rip scream_

There's a tear of flesh against teeth follows by a loud choking scream permeates in the air and oh, it's him. He's the one who screams in the night. Hiro thrashes as the creature above him takes another grub of a peel from his arm, evidently lapping herself (itself?) in pleasure at the oozing bite before bending down to take more bite-

_Hiro Hiro Hiro!_

"Hiro!" Someone screams - more like a roar. He swears even when he's littered in blood and wounds, he sees the way Tadashi - oh thank god he's all right - grabs the knife on the floor, switches on his foot and throws the knife into the air with a flick of his wrist.

The metallic object sings before it's embedded in the she-creature's skull. It plummets next to Hiro with a wordless thump.

He remembers clutching at his arm, purposely avoiding the missing skin. Here, he can only stare as Tadashi marches without a word toward the upcoming flock.

The weapon is still in his arms as he takes the first swing, guiding the blunt spot on the creature's cranium with an impeccable calibration. He shifts, edging away from the probing nails, meandering the hard object before he forces it on one of those…monsters. Two, three, swift hit before Tadashi flips the cudgel in his palm and flings it at the one speeding at him.

It hits.

The fallen creature snarls at him but Tadashi preoccupies himself by winding the neck of what used to be an old lady, cracking sound floats contemptuously. He watches the body fall, before he makes a sharp line for the previous fallen monster, observing it deeply before he lifts a foot and jabs it on the creature's scalp.

Again.

Again.

And again.

And again.

And again.

This is not his brother.

"Ta- Tadashi!" Hiro squeaks.

Whatever wild menace in his brother's gaze before, it's gone the moment it falls upon him.

"Hiro." Hiro blinks once. And he's already in his brother's embrace.

"I have you. It's okay. It's okay. We'll clean the cut. You're immune. You know it. We know it. It's okay."

Hiro can't tell who is Tadashi trying to placate; Hiro or himself.

He'll also ask what Tadashi means by immune later on.

"Oww!"

"Sorry sorry. I'm so sorry, Hiro."

After they're done tending to his wound.

"Hunters?" He questions.

So that's what they're called. Or what Tadashi's named them at least.

This man, stranger, copycat - gives Hiro a confused glance before he tries to splinter two small stones against one another, sending the quick sparks into the stock pile of charcoal and damaged timbers. They're still hiding in the empty house. It's a bit safer now. The growls and scratches are getting prominent because this Tadashi claims it's nightfall and they, the Hunters, are always active when the sun is down. Though, Tadashi swears they won't be getting in for now.

There's snow outside. It's cold but at least it's not hailing. Just a speck of white dots on the green and earth.

Hiro puffs his breathe, bringing the blanket Tadashi has given him closer to his small, shuddering frame. He draws closer to the now barely lit fire. The wound is now fully cleaned and bandaged. It stings but he'll survive. He still wants to know what Tadashi means by immune but the fatigue is vibrant at the tip of his awareness.

He also very much wants to know how he gets here and why. And when he says here, he means this…well, world.

(Hiro winces at the color of orange and red, and a little tint of blue. He hates the scorching heat but-)

"You okay?" Tadashi croons. He stands, slips on his height, stands up again and sits next to Hiro. The younger boy offers the thick blanket to the stranger. Tadashi smiles, obliging his wish but they're sharing the warmth, cuddling in the mast of old woolen.

What's going on? Where's everyone? Where's Aunt Cass? What is wrong with this world?

No really, world, what is wrong with you?

But-

Tadashi is here.

And he-

"I'm fine, Tadashi." Hiro fights the urge to scoot away. This man is his brother and still, he is not.

His brother is gone.

This man hurts and kills with terrifying ease.

Tadashi opens his mouth to say something. Hiro beats him to it. "What happened before? How did we get here?"

The copycat blinks at him. His mouth slightly slips open. Disbelief paints itself on his facial expression. Oh for the love- why this stranger looks like the exact paper print of his deceased brother? He can't reconcile with his feelings. Should he be happy? Angry? Both? Or naught with both of them?

"What do you mean how did we get here?" He sounds a little angry now. That's how Hiro's Tadashi sounds too. Or sounded. Pain grazes at his heart at the memory again. "Hiro, you jumped in a group of Hunters when you saw them chasing a young girl." He chides. There's a tone of disappointment and proud in his voice. Honestly, how can anyone feel both disappointed and proud at the same time? Only Tadashi can do that without sounding too odd.

(He should stop comparing copycat Tadashi to his Tadashi.)

(But it's hard.)

(Baymax I-)

Hiro casts a scowl at his broth- at this Tadashi. He wants to say that's what Heroes do but he's just a naive kid who thinks he can help people by putting himself and his friends in danger. And really, he doesn't watch too much anime lately to use that quote against the copycat with Tadashi's face.

He can't remember jumping into the herd but he retaliates anyway. "What was I supposed to do then? Let her die?"

Tadashi stops. He turns away and looks at the flickering fire. The orange-red dances in his dark irises.

(Hiro wants to tug him away from the blaze.)

"She did die." Tadashi says. Laments. His eyes are empty. "But it was on me. I had to make a choice then, to save you or her but it was never a choice at all. I didn't look twice at her," _screaming as she was scraped apart by nails and teeth, looking at me with a pleading look_ "When I went to you. After that, we just ran and they chased us until we found this place." Tadashi gestures around.

Hiro stays silent. He never stirs away from the man next to him. What's the right emotion for this kind of moment?

"I-." He gulps. "Thank you." It feels bitter on his tongue, thanking someone while the other dies in his place.

Tadashi takes the gratitude. He hunches, draping his arms around Hiro, bringing the smaller brother to his laps. Hiro doesn't bother fighting him. Their foreheads are touching; skin against skin and Hiro feels like he needs to cry this time. This is so Tadashi.

"We're used to it. To running, right?"

No. "Yes."

Tadashi sighs. "They won't stop hunting for you, Hiro. They'll search every corner and turn every rock if they have too. They'll never put a rest to it." Deep inhalation. "Hunters are predictable but you can never tell it with living people."

Wait, what? "What?"

There's a hushed of guilt in his voice when he speaks. Hiro wonders if Tadashi still blames himself for allowing him to get hurt. "You know I will always protect you, Hiro. Just please...have faith in me, Kay?" _I won't ever allow anything to take you away from me. _

This Tadashi is not his Tadashi.

Hiro prays he can still call him brother anyway.

**X**

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**Written by Wookie**

_**So here's the story: I very much want to continue it but after a look at it, twice, and thrice, I realize it doesn't come out the way I want it: proper enough to be read. However, this one has been in my folder for a while and rather than to let it rot in my dusty folder, I decide to let it decompose here. Aha.**_


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